N,N′-Bis(aryl)pyridine-2,6-dicarboxamide complexes of ruthenium: Synthesis, structure and redox properties

Dasgupta, Moutusi and Nag, Sumon and Das, Gopal and Nethaji, Munirathinam and Bhattacharya, Samaresh (2008) N,N′-Bis(aryl)pyridine-2,6-dicarboxamide complexes of ruthenium: Synthesis, structure and redox properties. In: Polyhedron, 27 (1). pp. 139-150.

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Abstract

Reaction of five N,N′-bis(aryl)pyridine-2,6-dicarboxamides (H2L-R, where H2 denotes the two acidic protons and R (R = OCH3, CH3, H, Cl and NO2) the para substituent in the aryl fragment) with [Ru(trpy)Cl3](trpy = 2,2′,2″-terpyridine) in refluxing ethanol in the presence of a base (NEt3) affords a group of complexes of the type [RuII(trpy)(L-R)], each of which contains an amide ligand coordinated to the metal center as a dianionic tridentate N,N,N-donor along with a terpyridine ligand. Structure of the [RuII(trpy)(L-Cl)] complex has been determined by X-ray crystallography. All the Ru(II) complexes are diamagnetic, and show characteristic 1H NMR signals and intense MLCT transitions in the visible region. Cyclic voltammetry on the [RuII(trpy)(L-R)] complexes shows a Ru(II)–Ru(III) oxidation within 0.16–0.33 V versus SCE. An oxidation of the coordinated amide ligand is also observed within 0.94–1.33 V versus SCE and a reduction of coordinated terpyridine ligand within −1.10 to −1.15 V versus SCE. Constant potential coulometric oxidation of the [RuII(trpy)(L-R)] complexes produces the corresponding [RuIII(trpy)(L-R)]+ complexes, which have been isolated as the perchlorate salts. Structure of the [RuIII(trpy)(L-CH3)]ClO4 complex has been determined by X-ray crystallography. All the Ru(III) complexes are one-electron paramagnetic, and show anisotropic ESR spectra at 77 K and intense LMCT transitions in the visible region. A weak ligand-field band has also been shown by all the [RuIII(trpy)(L-R)]ClO4 complexes near 1600 nm.

Item Type:	Journal Article
Publication:	Polyhedron
Publisher:	Elsevier Science
Additional Information:	Copyright of this article belongs to Elsevier Science.
Keywords:	N,N′-Bis(aryl)pyridine-2,6-dicarboxamide ligands;Ruthenium complexes;Redox properties.
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	25 Mar 2010 11:15
Last Modified:	19 Sep 2010 05:58
URI:	http://eprints.iisc.ac.in/id/eprint/26528

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